The present disclosure relates to a developing device incorporated in an image forming apparatus such as copies, printers, and facsimile machines. In particular, the present disclosure relates to a method for preventing developer from clogging in a gap between a developing roller and a regulating blade.
In one conventionally common process as an image developing method in image forming apparatuses using an electro-photographic process, powder developer is mainly used, an electrostatic latent image formed on an image carrying member such as a photosensitive drum is made visible with the developer, and the visible image (toner image) is transferred to a recording medium and is then fixed.
Developer is roughly divided into two-component developer containing toner and magnetic carrier and one-component developer containing non-magnetic or magnetic toner alone. As a developing method using magnetic one-component developer, a so-called jumping one-component developing method is known, according to which a fixed magnet member having a plurality of magnetic poles is arranged inside a developing roller, toner in a developer container is carried on the developing roller by use of a magnetic carrying force, a thin layer of toner is formed through layer thickness regulation by use of a regulating blade, and toner is made to fly to a photosensitive drum at a developing position.
In recent years, low-melting-point toner is increasingly used for energy saving and acceleration of printing. When continuous printing is performed in a high-temperature environment by use of low-melting-point toner, toner stagnating at a place where the developing roller and the regulating blade face each other (regulating portion) softens due to heat or mechanical stress and causes blocking, resulting in clogging in a gap in the regulating portion. This inconveniently results in unevenness in a toner layer on the developing roller, producing vertical streaks such as white streaks and gray streaks on the output image.
To avoid that, for example, toner and a developing system excellent in low-temperature fixability, high-temperature-resistant offset property, and blocking resistance have been developed. According to one known method, the regulating height of the regulating blade in opposite end parts thereof facing near opposite end parts of the developing roller is set higher than in other parts, and thereby compression (high density) of developer in the opposite end parts of the developing roller is reduced, in order to thereby prevent developer agglomeration.
According to another known method, the angle of arrangement of a magnetic field generating means having a plurality of magnetic poles arranged inside the developer carrying member is changed according to the use environment of and the manner of use of the image forming apparatus, in order to thereby improve degraded image quality resulting from lowered image density and fogging due to a white part.